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2 Sheets-Sheet 1 A. E. KEITH RELEASE FOR AUTOMATIC TELEPHONE SYSTEMS Filed Jan. 15 1905 March 23 ,1926.

March 23 ,192. 1,578,017

A. E. KEITH RELEASE FOR AUTOMATIC TELEPHONE SYSTEMS Filed Jan. 13, 1905 2 Sheets-Sheet 2 WIT/V5555? flTTOE/VEYS,

vt z'itented Mar. 23, 1926.

ALEX-human KEITH, r CH Aem-tw me ess cuoe, MESNE'ASSIQNMENES? monumouerxc ELEGTMG'INQ, or CHICAGO, ILLINQIfi, A GQEBQBATIOIN or em- :WARE.

f nunnnsn mm AUKFOMA'IIC rnnnrnonn sysrnm's.

pn iee ien di nu t y 1 1 11 5 1141 Ne 40 969- useful lniproye nent in Releases fgr Auto:

iebi Telephone Syst ms; f hic t e foleu'iiie' s epe i i e ie t 1 win be eadily n r wed tha my nvention relates to that 'parti'culnr type of eutome ic t ephqnc y m n wh h 62t suhscriher'is provided with means 15; ele tr eel'il nu s'o e th ine t he xcha ge 9 2 el teti n+ hat i to s or 9 1% a met l breek actio i h 1 1 1 mut -and. whi h se tr mpulses; c rc pend ne t9 t umbe f h called subs fiber;e erc'c e y a t yep' e tomatic w t h n appara able ted toresppnd to the impulses or makew en: ectio gbr ug out b t e u scjrihertmtd to eutoin atic ally establish con-' ecticltwi hthe'liiw eedine' o h elled Subari ets tet ne The'p t cu e switch h ece ves the im se r imp e re ondng .tethe "first digit 9f th alled um er is erm d first seem; hile h s t which then receives the'inipulses representing he s wed ill c 9f "the 1 el e numbe is termed ed el'ei tof; nd as 31. 11 lectors may be e nployedfaccord ng' to the ize fi ths excha ge the number c d t involved in the hlghest numberns'mey be found necessary or desirable. 'The switch' mp e edv .f r with "t e nelc nn' ti n ifi UYTW- th h fl r b ri lin and receives the impulses correspondee m the 12 1 ve di ts 9f the a d number, istey fl a -connectcra My i n' vention' involves an arrangement by," which th ii e 1n t c n be em e'y y th ceiling s1'1bs';c"iher when the conversation alsodescribed and claimed a IlOvel arrungeme it whe eby the s d s cond selector,

it Swit hes- #159, ac we, h ea circuit between the switches includes the private-wiper and private hank-contact-s of the selector to be relegtsed. But for the breeder purposes of'niyinvention I do net li nit nyself to any particularnumher of switches, or to any particular a-rrengenient for disconnecting the relay bridges during conversation, or to any particular arrangeinentior releasing in such a,

l s obvious that with un arrangement of this che'ra cter the'systein may involve afirst and seccn d*selecto i" oirany nuinber of se lectors, together with a c'onnect oi and that no coils, either in series or in bridge, need heleft in the circuit at the difierent selectors, the talking circuit bein free from inductive'resistance, either in Bridge or in series,'betw.een the tritnsniitting and receiving ends of the circuit, with the two exceptions of the verticaW'and rotary relays of the connector, and the-beck releese-relztys of the connector, it being Qt): vious that these relays, or some equivalent arrengenienh'nnist he left across the talking circuit, the iorin'er in order to-lnake it pos-' sible for the calling or called subscriber, for example, torelease" or restorethe different switches after the conversation'isterminated; and the letter to enable a called subscriber to disconnect 51; connector-connected with his own line, he so desires.

The nature and advantages of my inven; tion will, however, hereinafter more fully appear.

In the accompanying "drawings Fig. 1 is at diagramillustrating the con'ditionof the apparatus during the time the calling subscriber is conversing-with the called 'suhscrilo er and showing the apparatus at the calling subscrihers station connected, through the inediu n of a' first 'selector; with tr nk 'ne l adin t 0 l' tc j, and through the nediu in of said second selector with n trunk line leading to econ ee e'r he h e il n s icati t e t lking circuit, and the other or light lines indicating the auxiliary circuits employed for pe at ng d t eren sw tc e a e varieus other purposesg F129 2, lm la t Fe 1 i h th We tion that it represents a connection in an exchange of a larger capacity than that shown in Fig. 1.

As thus illustrated, A represents the apparatus or equipment at the calling subscribers station. E represents the first selector at the exchange or central station, and C the second selector at the same plac..

D represents the connector at the exchange or central station. E represents a second. selector having bank contacts which are multipled with those of the second selector C. It will be understood, of course, that these automatic switches can be arranged at the same station, or at different stations.

Atthe subscribers station-A the switch a is employed for grounding first one side and then the other of the subscribers line, so as to produce the electrical impulses corresponding to the number called. As will hereinafter more fully appear, the switch a is used by the subscriber for rounding both sides of the line, so as to re ease or restore the switches after the conversation is terminated. The telephone set, comprising the transmitter a andthe receiver a, may be of any suitable, known or approved character.

As shown, the subscribers line 1 has connection with the wipers b and if of the so called side switch of the first selector B. This first selector may comprise the usual vertical and rotary relays b and b the private magnet Z), the release magnet b and may also comprise the release relay 6 de scribed in my said former application. Other familiar features of a first selector of this character consist of the private wiper b of the said side switch, and the private, vertical and rotary wipers b 1) and 5 on the switch shaft, together with the private, vertical and rotary bank contacts I), I) and b.

The second selector C comprises the usual vertical and rotary relays c and 0 the private magnet 0 and the release magnet 0 The release relay 0 is a new feature in a second selector of this character, as is also the resistance coil There are also certain novel features in this second selector,

as will hereinafter more fully appear; but' other familiar elements of a switch ofthis character consist of the vertical and rotary wipers 0 and 0 of the side switch, and the private, vertical and rotary wipers c 0" and 0 on the rotary switch shaft. The private, vertical and rotary bank contacts 0 0 and 0 are also included, as usual, in the construction of the said secondselector.

The connector may include the usual backrelease relays d and al the vertical and lotary relays d and (Z the private magnet d and the release magnet The resistance coil d", described in my former application, is also a feature of the said connector,

which latter is further identified by the private, vertical and rotary wipers d", d and d of the side switch. Other familiar elements in a connector of this character consists of the condensers 03 and (i ar 'anged in opposite sides of the talking circuit between the vertical and rotary relays and the back-release relays. Like other connectors of this character, the rotary switch shaft is provided with private, vertical and rotary wipers (Zfld and d, and with the corresponding private, vertical and rotary bank contacts (5 (Z and It".

At the other second selector E the private,

vertical and rotary bank contacts 6, e and e are multipled, as shown, with the private, vertical and rotary bank contacts, respectively, of the second selector G. Only the release relay e the private magnet e and the private wiper e of the side switch are shown at the point where the said second selector E is supposed to be located, together with the private, vertical and rotary wipers e, c and e of the rotary switch shaft.

Between the first and second selectors the connection consists of the main trunk line conductors 2 and 2, and of the third or additional trunk line conductor 3. In a simi ar way the connection between the second selector and the connector consists of the main trunk line conductors 4 and 4, and the third or additional trunk line conductor 6.

Thus, between the first and second selectors there are three trunk line conductors,

two to be used for talking, switching and signaling purposes, and the. third to be used for releasing purposes after the conversation is terminated. And .in like manner, there are three trunk line conductors between the second selector and the connector, two to be used for talking, switching and signaling purposes, and the third'to be employed only for releasing purposes after the conversation is terminated.

As illustrated, the apparatus is in the condition necessary for talking purposes, and, assuming the conversation to have been terminated, the calling subscriber may then release or restore the different switches in the following manner: The switch a is first operated at the calling subscribcrs station, so as to simultaneously ground both sides of the line and connect the two sides together. This, of course, will result in energizing the vertical and rotary relays (F end d at the connector D. It will also result in the energizing of the private magnet (Z the circuit of this magnet having been closed by the energizing of the relay cl"; The relay d and the private magnet cl", when energized, effect the closing of a circuit including the release magnet It will be seen that all of these energizing circuits, when thus closed, include the battery F and the bus bar or common connection fwith which one pole of the battery is connected, and also include the ground or common connection 7 with which the other pole of the battery is connected. The release magnet (Z when energized, closes the switch (Z and thus closes a ground circuit including the said battery,

the resistance coil cl, the private wiper c c and the consequent closing of the switch 0 controlled by said magnet. A circuit is then formed from the battery through the bus bar and the coil 0 through the trunk line conductor 3, through the private bank contact 6 through the private wiper b and thence through the coil of the release relay 6, and through the private wiper b of the side switch to ground and back to the battery. The release relay 6, when thus -energized, closes the switch 6 and thereby completes a circuit from battery through the bus bar and the coil of the release magnet 5 and thence to ground and back to the battery. In this way the energizing of the permanently bridged coils (Z and (Z results in a series 01"- operations, commencing at the connector and extending back over the trunk line connections to the first selector. The release magnets of the connector, second solector and first selector, when energized, eti'ect a release of the three switches, through the medium of any suitable, known or approved devices. The release relays of the first and second selectors are preferably low wound, while the coils c and (Z are of, say, one hundred chins resistance. The private magnet, however, may be of three hundred and fifty ohms resistance. In this way the resistance of the said private magnets is sufficient to prevent the energizing of any release relays which may be momentarily included in circuit therewith, as might be the case if a third subscriber should attempt to use the second selector E during conversation between the calling and called subscribers. The resistance of the coils c and d is sufficient to maintain the necessary guarding potential at the private bank contacts D and o In other words, the resistance furnished by these coils, and interposed between the negative pole of the bat tery and said cont-acts, is much more than any resistance which may be included in the connections between the positive pole of the battery and the said private bank contacts. Consequently theregis always a guarding potential of a positive character at the said private bank contacts.

It will be readily understood that the energizing of the different magnets in the connector, second selector and first selector occurs practically at the same time, all three switches being released practically as soon as the calling subscriber operates the switch o During conversation between the subscribers there are no coils in series in the talking circuit, and there are no coils in bridge of the talking circuit at the calling side of the condensers, with the single exception of the coils (Z and (Z Thus the efiiciency oi the talking currents is in no way interfered with, and at the same time ample and effective provision is made whereby the calling subscriber may release or restore the switches as soon as the conversation is terminated. The private wipers on the s witch shafts of both the first and econd selectors have the double function, so to speak, of establishing a guarding potential at the contacts of the private banks, and oi closing one of the normally open switch points in the release circuits. The

' connector releases the second selector over a third or additional trunk line conductor, and the second selector releases the first selector over a third or additional trunk line conductor. The release magnet of the connector used for releasing the connector and for closing a normally open switch point in the release circuit of the second selector. In a similar way the release magnet of the second selector is used for closing a normally open switch point in the release circuit of the first selector. The release relay, howevt of the second selector controls it nor: y open switch point in the release magnet circuit of the second selector; but the release magnet of the second selector both controls a release circuit in cluding a release relay, and is itself in turn controlled by another release relay. In this way the process of connecting up a calling subscriber with a called subscriber proceeds in one direction, while the operation oi? making a disconnection starts at the other end of the train of connections and proceeds in the opposite direction.

The talking circuit shown is, of course, normally can. The relays 7) and b are normally in bridge across coinluctors of said The circuit, as are also the relays c and c plurality oi? bridges thus provided are, how

Evi-

7 first selector.

the talking circuit is completed, and while the subscribers are talking, there are only three bridges across the circuit, to-wit, the bridge containing the coils (Z and (Z the bridge containing the coils cl and W, and the bridge 5 b of the called subscribers The bridge containing the coils (Z and (Z ean be omitted it such is desired.

As previously stated, Fig. 1 represents a connection in an exchange employing first selectors, second selectors and connectors. In such a system the numbers of the lines would comprise four digits and the exchange would have a maximum capacity of ten thousand lines. It it is desired to provide an exchange of a larger capacity it is evident that all that is necessary is to insert additional selector switches between the second selectors and connectors. By adding socalled third selectors the capacity of the exchange is increased to one hundred thousand. .Fig. 2 represents a connection in such an exchange. The substation A, first selector 15, secoi'id selector C and connector D are the same as shown in Fig. 1 and are given the same reference numerals. The third selector G is in all respects the same as the second selector C. In such a system it is evident that the release takes place in practically the same manner as the release in the system shown in Fig. 1, the only difference being that the release magnet (Z of the connector operates to close the circuit of the release relay o't the third selector G instead of that of relay 0" of the second selector 0, and the circuit of said relay 0 is closed by the release magnet g of the third selector G instead of by the release magnet of the connector.

From the foregoing it ,will be seen that this system may readily be extended to any desired size by simply adding additional selectors similar to the selector C.

\Vherevcr I use the expression metallic circuit. trunk line I mean a trunk line .in which there is a metallic circuit tor talking purposes, in contradistinction to a talking circuit in which but a single conductor is employed with. a ground return; for example, the trunk line which extends between the first and second selectors I call Q'D'IGtELIllO circuit trunk line, even though a grounded.

plying all necessary current, said second selector being provided with a releasemagnet controlling a normally-open switchpoint in the said release-circuit.

2. An automatic telephone system comprising a first selector, a second selector and a connector, a release-circuit for the second selector, a release-circuit for the first selector, together with means for supplying all necessary current, the connector having a release-magnet controlling a normally-open switch-point in the releasecircuit of the second selector, and the second selector having a release-magnet controlling a normally-open switch-point in the release-circuit of the first selector.

3. An automatic telephone system comprising a plurality of selectors, trunk-line connection between said selectors, said trunk-line connection including a pair of main conductors, and an additional or third trunkline conductor, a connector having trunk-line connection with the said selectors, said connector trunk-line connection including a third or additional trunk-line conductor, a release-circuit for the first selector including one of said additional trunk-line conductors, a release-circuit for the second selector including another of said additional trunk-line conductors, together with means for supplying all necessary current, said connector being provided with an electro-magnet adapted to control a normally-open switch-point in the release-circuit of the second selector, and the said second selector being provided with an electro-magnet controlling a normally-open switch-point in the releasecircuit of the first selector.

41-. An automatic telephone system comprising a plurality of automatic step-bystep selective switching machines, each machine having a release-circuit, the release-circuit of one machine being provided with a normally-open switch-point located in another machine, the said other machine being provided with an electro-magnet controlling said switclnpoint, and wit-h a relay controlling the said electro-magnet, a trunk talking circuit extending through all oi said switching machines, means for supplying all necessary current, and a trunk conductor in cluded in each release circuit.

5. An automatic telephone system com prising a. plurality of selectors, a connector, a release circuit for each selector, the connector being provided with elect-ro-magnetic means: for controlling the releasecircuit of a selector, and each select-or except the first one being provided with electro-magnetic means for controlling the release-circuit of another selector, together with means for supplying all necessary current.

6. An automatic telephone system comprising a normally-open talking circuit, subscriber-operatedmeans for closing said circuit for talking purposes, including a plurality of bridges normally connected across said circuit, and means for successive ly cutting off or opening said bridges when said circuit is closed, said circuit being at all times free from inductive resistance in the path of the voice currents.

1 7. An automatic telephone system comprising a selector having release mechanism, a release-magnet adapted to operate said mechanism when energized and de-energized, a trunk-selecting switch mechanism provided with releasing means, a. release circuit controlling said releasing means, and normally open contacts included in said release circuit and operated by said magnet. 8. An automatic telephone system comprisinga first-selector provided with releasing means, a release-circuit controlling said releasing means, a second-selector provided with release mechanism, an electro-magnet for operating said mechanism, normally open contacts included in said circuit and operated by said magnet, and a centralized source of switching current.

9."In a telephone system, the combination of a switching machine provided with release mechanism, an electro-magnet for operating said mechanism, another machine provided with release mechanism, a releasemagne t'and a release-relay, a third machine provided with releasing means, a circuit for said relay controlled by said electro-magnet a circuit for said release-magnet controlled by said relay, a circuit for said releasing means controlled by said release-magnet, and

a centralized source of switching current.

10. In a telephone system, a connector and a plurality of selectors connected up in series and provided with release-magnets, a talking circuit, means for initiating a release of the connector over the talking circuit, and means independent or the talking circuit for completing the release from the connector back through the second and first selectors. i

11. In a telephone exchange system, the combination of a talking circuit, a series of bridges on the conductors" of said circuit, means for cutting off a plurality of said bridges, and means for retaining one of said bridges during talking for releasing purposes.

12. In a telephone exchange system, the combination of a talking circuit, a series of bridges on the conductors of said circuit, means for cutting off a plurality of said bridges, trunk release circuits, and means for retaining one of said bridges during talkin to control said release circuits.

13. In a tele hone exchange system, the combination 0 telephone lines, automatic means for trunking calling lines in eoaaee selectors;

tion with called lines, comprising a series of bridges across the conductors of any talking circuit provided between calling and called subscribers, means for cutting oii a plurality of said bridges, releasing means for disconnecting between subscribers, and means for retaining one of said bridges to enable a subscriber on a talking circuit to control said releasing means.

14. In a telephone exchange system, the combination of a talking circuit, a series of bridges on the conductors of said circuit, and automatic means for successively removing a plurality of said bridges.

15. In a telephone exchange system, the combination of a talking circuit, a series of bridges on the conductors of said circuit, line relays in said bridges, circuits controlled by said relays, automatic means for cutting oii a plurality of said bridges, means for retaining one of-said bridges during talking, and releasing means controlled by the said retained bridge or bridges.

16. In a telephone exchange system, the combination of a talking circuit, a series of bridges on the conductors of said circuit, electromagnets in said bridges, automatic means for cutting oif a plurality of said bridges, and means for retaining one or more of said bridges during talking.

17. In a telephone exchange system, the combination of a talking circuit, a plurality of selectors in said circuit, a connector in said circuit, the selectors and connector having bridges on the conductors of said circuit, automatic means for cutting ofi the bridges'ot "the selectors, and means for retaining the bridge or bridges of the connector.

"18.In a telephone exchange system, the combination of selectors, trunk lines leading therefrom, means in said selectors for selecting idle trunk lines, other selectors at the ends of said trunk lines, other trunk lines leading from said other selectors, means in said other selectors for selecting idle trunk lines, each trunk line comprising a pair of voice-current conductors and a third or special conductor for purposes other than talking. r v

19. In a telephone exchange system, the combination of a plurality of selectors,- three-wire trunks for connecting said selectors together, and subscriber-controlled means ahead of the selectors for releasing the same over the third wire of said trunks.

20. In a telephone system, a calling line and a called line, means including a plurality of automatic trunk selectors for extending connection from the calling line to the called line, a trunk release circuit over which the second-selector releases the firstselector, and means ahead of the second selector for controlling the release ot'both 21. In a telephone system, a plurality of first-selectors and second selectors, each first selector adapted and operative to seize an idle trunk leading to a second-selector, means by which the second-selector is operative to release any first-selector over a conductor of said trunk, and means ahead of the second selector for controlling the release of both selectors.

22. In a telephone system, an open tall ing circuit, a plurality of bridges across said circuit, means controlled by said bridges-tor automatically and progressively establishing said circuit, means for cutting a plurality of said bridges before reaching the called line, and means for releasing over trunk conductors by means of a bridge retained across said circuit for that purpose.

23. In an automatic telephone trunking system, means whereby idle trunks are automatic'ally selected in accordance with the first and second digits of any called number, including a central station, a substation connected therewith through a metallic circuit line, a source of current, a selector controlling magnet at the central station for connection with said line, and an electrically operative device the operating circuit oi which is controlled by said controlling magnet for causing disconnection of said controlling magnet from the circuit.

24:. Ina telephone trunking system, means whereby idle trunks are automatically selected in accordance with the first and second digits of any called number, including a metallic circuit line, a selector for said line, a controlling magnet for said selector normally bridged across the talking circuit of said line, a source of current connected between said magnet and ground, means at said substation for completing connection between said line and said third conductor for energizing said magnet, a side switch for said selector adapted to disconnect said magnet from said line, a relay at the central ofiice for controlling said side switch, and means at the substation for energizing said relay to cause the operation of said side switch to disconnect said first magnet from said line, substantially as described.

25. In an automatic telephone trunking system, means whereby idle trunks are automatically selected in accordance with the first and second digits of any called number, including a metallic circuit subscribers line, a metallic circuit trunk line to which said subscribe'rs line is adapted to be extended, selecting switches for said subscribers line and said trunk line, controlling magnets for each of said selecting switches normally connected respectively with said subscribers and trunk lines, a side switch for said subscribers selecting switch adapted to disconnect its controlling magnets from the sub scribers line, means for causing the selecting switch of said'line to connect said line with said trunk, and to simultaneously. disconnect said controlling magnets from said line, substantially as described.

26. In an automatic telephone trunking system, means whereby idle trunks are automatically selected in accordance with the first and second digits of any called number, including two subscribers lines extending to a central olfice, a first selector for one of said lines, a trunk line, a second selector therefor, another trunk line, a third selector therefor, controlling magnets for each selector, a trunk line leading from said third selector, a connector, controlling magnets for said connector, means for causing the first selector to automatically select and con nect with said first trunk line, means for causing said second selector to automatically select and connect with said second trunk line, means for causing said third selector to automatically select and connect with said third trunk line, means for connecting said third trunk line with the second subscribers line, and means for automatically rendering the controlling magnets of said first and second selectors inoperative when said selectors have performed their selective function, substantially as described.

27. In a telephone trunking system, means whereby idle trunks are automatically selected in accordance with the first and second digits of any called number, including a pair of subscribers lines, connected by trunk lines at a central ofiice, automatic selecting devices for said subscribers lines, and for each of said trunk lines, a pair of controlling magnets bridged across said metallic circuit line at one of said selecting devices, means under control of said magnets for causing all of said selecting devicesto return to their normal position and break the connection between said subscribers lines and said trunk lines, substantially as described.

98. In an automatic telephone trunking system. means whereby idle trunks are automatically selected in accordance with the first and second digits of anv called number, including a subscribers line, a selecting switch for said line at a central oilice, a trunk line to which said SHbSCIlbCITS line is extended by the movementof the selecting switch of said subscribers line. a selecting switch for said trunk line, a pair of controlling magnets for each of said selecting switches adapted to control the selecting movements of said switches, the magnets at the selecting switch of said subscribers line being in an open bridge across said subscribers line during a connection between said line and said trunk. said magnets in the sclooting switch of said trunk being connected in a closed bridge across said trunk during a connection with said line, and means associateo with the selecting switch of said line and controlled by the bridged magnets ot' the selecting switch of said trunk to cause the selecting switch of said line to assume its normal position, disconnecting said line from said trunk, substantially as described.

29. In an automatic telephone trunking system, means whereby idle trunks are automatically selected in accordance with the first and second digits of any called number, including a built-up circuit between two subscribers lines, selecting switches and trunk lines involved in building up said circuit, controlling magnets connected with said circuit at some of said selecting switches, thcr controlling magnets disconnected from said circuit at other of said selecting switches, and means at the switches having connected magnets for causing those switches having disconnected magnets to disconnect said built-up circuit, substantially as described.

80. In an automatic telephone trunking system, means whereby idle trunks are automatically selected in accordance with the first and second digits of any called number, including a subscribers line, a first selector therefor, selecting contacts for said first selector, a trunk line adapted to be connected to said subscribers line by said first selector, a second selector for said trunk line, controlling magnets at said first and second selectors, means for energizing the magnets of said first selector to move said selecting contacts into engagement with said trunk line, a switch actuated by said magnets during their selecting operation to disconnect said magnets from said line, a release magnet for said first selector, a separate conductor individual to said trunk line, and means controlled by the magnets of said second selector for causing the operation of the release magnet of said first selector over said separate conductor, substantially as described.

31. An automatic telephone trunking system, means whereby idle trunks are auto matically selected in accordance with the first and second digits of any called number, including a temporarily established talking circuit, a selector relay bridge temporarily disconnected or cut off from the said circuit, and a connector relay bridge retained across the said circuit for releasing purposes, together with selector and connector rel-easing means controlled by the said connector relay bridge. a

32. In a telephone exchange trunking system, means whereby idle trunks are auton'iatically selected in accordance with the first and second digits of any called number, including a talking circuit, a plurality of bridges on the conductors of said circuit an tomatic means for reducing the number of bridges, releasing'means for disconnecting subscribers, and means for retaining one of said bridges duringtalking to control (he said releasing means.

33. In a telephone exchange trunking system, means whereby idle trunks are automatically selected in accordance with the first and second digits of any called number, including telephone lines, automatic means tor trunking a "ailing line into connection with a called line to form a talking circuit, a bridge over the conductors of said circuit, and automatic means "for cutting old or opening up said bridge during talking.

34:. In an antoi'natic telephone system, a metallic circuit subscribers line, a first selector therefor, a trunk line to which said first selector is adapted to extend said ibscribei"s line, a second selector for said trunk line, a second trunk line to which said second selector is adapted to extend said first trunk line, a third selector for said 0nd trunk line, operating magnets for each selector for controlling said selectors in extending the circuits of their respective lines, and a switch for said first and second selectors under control of said magnets for dis connecting said magnets from said lines after they have performed their operating functions, substantially as described.

In an automatic telephone system, a metallic circuit subscribers line, a first selector therefor a trunk line to which said first selector is adapted to extend said snb scribers line, a second selector for said trunkline, a second trunk line to which said second selector is adapted to extend said first trunk line, a third selector for said second trunk line, operating magnets for each selector for controlling said selectors in extending the circuits of their respective lines, a switch for said first and second selectors under control of said magnets for disconnecting said magnets from said lines after they have performed their operating functions, and means under control of said third select-or for causing said first and second selectors to discontinue the extended connections between said subscribers line and said trunk lines, substantially as described.

86. In a telephone system, two subscribers telephone lines, a first selector for one of said lines, a connector in which the other said line terminates, a second and a third selector, two trunk lines terminating re spectively in said second and third selectors, a third trunk line terminating in said connector, means under the control oisaid first subscribefs line for causing said first selector to automatically select and connect with the trunk line terminating in said sece-nd selector, for causing'said second selector to automatically select and connect with the trunk line terminating in said third selector, for causing said third selector to automatically select and connect with said trunk line extending to said connector, and for causing said connector to select and connect with said second subscribers line, controlling magnets for said selectors, and automatic means in commotion with said first and second selectors for opening the circuit of the controlling magnets of said selectors, substantially as described.

37. In a telephone system, two subscribers telephone lines, a StlGCtlllQ' switch for one of said telephone lines, waiting connection terminals for the other o't said telephone lines, a. plurality of trunk lines, a line selecting switch for one Ofl said trunk lin s, trunk selecting switches for the other trunk lines, electroii'iagnctic controlling mechanisms under the control of said first subscriber :lor operating said selecting switches to successively select and connect said trunk connecting switches reria 1y with said first line, electromagnetic means for causing the lines selecting switch of the last selected trunk line to select and connect with the waiting tern'iinals of said second subscribei"s line, electromagnetic switch mechanisms for controlling the circuit of the electromagnetic selector mechanisms, a circuit for said electromagnetic switch mechanisms, said circuit being controlled by said electromagnetic controlling mechanisms, and means for restoring all of said selecting switches to their normal positions, substantially as described.

38. In an automatic telephone system, a telephone line, a selecting switch for said line at a central station, a trunk line to which said line is extended by said selecting switch, a selecting switch for said trunk line, controlling magnets for each of said selecting switches, said magnets oi the switch of said line being disconnected from said line during the connection of said line with said trunk, said magnets of the switch of said trunk being operatively connected with said trunk during said connection, and

means associated with said selective switch of said line controlled by the magnets of said trunk to cause the disconnection of said line from said trunk, substantially as described.

39. In an automatic telephone system, a subscribers line, a selecting switch for said line at a central ollice, a trunk line to which said snbscribers line is extended by the selecting switch of said subscribcfls line, a seby the bridged magnets ot' the selecting switch of said trunk to cause the disconnection of said line from said trunk, substantially as described.

40. In an automatic telephone system, a subscribers line, a trunk line, selecting switches for said subscribefls line and for said trunk line, a pair of controlling magnets for the selecting switch of said subscribers line bridged across said subscribers line, means for energizing said magnets to cause said selecting switch to select and connect with said trunk line, automatic means for disconnecting said controlling magnets from said line when said selection and connection is accomplished, a pair of controlling magnets bridged across said trunlr line, means under the control of the subscribers line for energizing said magnets, and means controlled by the simultaneous operation of said latter magnets to looting switches, release magnets for all of said selecting switches, means for energizing said bridged controlling magnets to operate the disconnect magnets of their own and of the other selecting switches involved in making the connection, substantially as described.

42. In an automatic telephone system, a subscribers line, a first selector therefor, selecting contacts for said first selector, a trunk line adapted to be connected to said subscribers line by said first selector, a second selector for said trunk line, controlling magnets at said first and second selectors, means for energizing the magnets of said first selector to move said selecting contacts into engagement with said trunk line, a switch actuated by said magnets during their selecting operation to disconnect said magnets from said line, a releasemagnet for said first selector, and means controlled by the bridged magnets of said second selector to operate the release magnet of said first selector, substantially as described.

43. In a telephone system, a metallic circuit line, a selector for said line, a controlling magnet for said selector normally bridged across the talking circuit of said line, a third conductor, a source of current connected between said magnet and said third conductor, means at said substation for completing connection between said line and said third conductor for energizing said magnet, a side switch for said selector adapted to disconnect said ma net from said line,

a relay at the central ofiice for controlling said side switch, and means at the substation for energizing said relay to cause the operation of said side switch to disconnect said first magnet from said line, substantially as described. I

44. In an automatic telephone system, a metallic circuit subscribers line, a metallic circuit trunk line to which said subscribers line is adapted to be extended, selecting switches for said subscribers line and said trunk line, controlling magnets for each of said selecting switches normally connected respectively with said subscribers and trunk lines, a side switch. for said subscribers selecting switch adapted to disconnect its controlling magnets from the-subscribers line, means for causingthe selecting switch of said line to connect said line with said trunk, and to simultaneously disconnect said controlling magnets from said line, substantially as described.

45. In an automatic telephone system, two subscribers lines extending to a central office, a first selector for one of said'lines, a trunk line, a. second selector therefor, another trunk line, a third selector thereto-r, control-' ling magnets for each selector, a trunk line leading from said third selector, av connector, controlling magnets for said connector, means for causing the first selector to automatically select and connect with said first trunk line, means for causing said second selector to automatically select and connect with said second trunk line, means for causing said third selector to automatically select and connect with said third trunk line, means for causing the connector to automatically connect said third trunk line with the second subscribers line, and means for automatically rendering the controlling magnets of said first and secondselectors inoperative when said selectors haveperformed their sclective function, substantially as described.

46. Ina telephone system, a pair of subscribers lines including a metallic circuit connected by trunk lines at a centralofiice, automatic selecting devices for said subscribers lines, and for each of said trunk lines, a pair of controlling magnets bridgec across said metallic circuit line at one 01"" said selecting devices, and means under control of said magnets for causing all of said selecting devices to return to their normal posit-ion and break the connection between said subscribers lines and said trunk lines, substantially asdescribed.

47. In an automatic telephone system, a subscribers line, a selectingswitch for said line at a central ofiice, a trunlr'line to which said subscribers line is extended by the, movement of the selecting switch of 'said subscribers line, aselecting switch for said trunk line, a pair of controlling magnets for each of said selecting switches adapted to control the selecting movements of said (lit. 9

switches, the magnets atthe selecting switch of said subscribers line being in an open bridge across said subscribers line during a connection between said line and said trunk, said magnets in the selecting switch of said trunk being connected in a closed bridge across said trunk during a connection with said line, and means associated with the selecting switch of said line and controlled by the bridged magnets of the selecting switch of said trunk to cause the selecting switch of said line to assume its normal position, disconnecting said line from said trunk, substantially as described.

48. In an automatic telephone system, a built-up circuit between two subscribers lines, selecting switches and trunk lines involved in building up said circuit, controlling magnets connected with said circuit at one of said selecting switches, other controlling magnets disconnected from said circuit at other of said selecting switches, and means at the switch having connected magnets for causing those switches having disconnected magnets to disconnect said builtup circuit, substantially as described.

49. In an automatic telephone .system, a subscribers line, a first selector therefor, selecting contacts for said first selector, a trunk line adapted to be connected to said subscribers line by said first selector, a second selector for said trunk line, controlling magnets at said first and second selectors, means for energizing the magnets of said first selector to move said selecting contacts into engagement with said trunk line, a switch actuated by said magnets during their selecting operation to disconnect said magnets from said line, a release magnet for said first selector, a separate conductor individual to saidtrunk line, and means controlled by the magnets of said second selector for causing the operation of the release magnet of said first selector over said separate conductor, substantially as described.

50. An automatic telephone system comprising a temporarily established talking circuit, a selector relay bridge temporarily disconnected or cut off from the said circuit, and a connector relay bridge retained across the said circuit for releasing purposes, together with selector and connector releasing means controlled by the said connector relay bridge.

51. In an automatic telephone system, a central station, a substation connected therewith through a metallic circuit line, a source of current, a selector controlling magnet at the central station for connection with said line, an electrically operative device the operating circuit of which is controlled by said controlling magnet for causing disconnection of said controlling magnet from the, circuit, a set of selector line wipers opera tive in accordance with an intermediate digit of the called number, and a set of connector line wipers operative in accordance with two digits of the called number to find the called line.

52. In a telephone system, a metallic circuit line, a selector for said line, a control.- ling magnet for said selector normally bridged across the talking circuit of said line, a third conductor, a source of current connected between said magnet and said third conductor, means at said substation for completing connection between said line and said third conductor for energizing said magnet, a side switch for said selector adapted to disconnect said magnet from said line, a relay at the central office for controlling said side switch, means controlled at the substation for energizing said relay to cause the operation of said side switch to disconnect said first magnet from said line, a set of selector line wipers operative in accordance with an intermediate digit of the called number, and a set of connector line wipers operative in accordance with two digits of the called number to find the called line, substantially as described.

53. An automatic telephone system comprising a temporarily established talking circuit, a selector relay bridge temporarily disconnected or cut off from the said circuit, a connector relay bridge retained across the said circuit for releasing purposes, together with selector and connector releasing mean. controlled by the said connector relay bridge, a set of selector line wipers operative in accordance with an intern'iediate digit of the called number, and a set of connector line wipers operative in accordance with two digits of the called number to find the called line.

54. In a telephone exchange system, the combination of a talking circuit, a plurality of bridges on the conductors of said circuit, automatic means for reducing the'number of bridges, releasing means for disconnecting between subscribers, means for retaining one of said bridges during talking to control the said releasing means, a set of selector line wipers ope 'ative in accordance with an intermediate digit of the called number, and a set of connector line wipers operative in accordance with two digits of the called number to find the called line.

55. In a telephone exchange system, the combination of telephone lines, automatic means for trunking a calling line into connection with a called line to form a talking circuit, a bridge over the conductors of said circuit, automatic means for cutting off or opening up said bridge during talking, a set of selector line wipers operative in accordance with an intermediate digit of the called number, and a set of connector line wipers operative in accordance with two digits of the called number to find the called line.

56. In an automatic telephone system, a subscribers line, a metallic circuit trunk line, a selector serving to connect said subscribers line with said trunk line, controlling magnets :for said selector, switches operated by said controlling magnets to open the circuit of said magnets upon the completion of a selection, and electromagnet mechanism controlled over the line circuit to actuate said selector to disconnect said subscribers line from said trunk line.

57 In an automatic telephone system. a subscribers line, a selecting switch therefor, a trunk line, controlling magnets normally bridged across the subscribers line for causing said switch to select and connect with said trunk line, means for automatically disconnecting said controlling magnets from said line after their operation, a source of current adapted to supply current over said trunk line to said subscribers line, and means operated by current from said source over said trunk line to cause said switch to disconnect said subscribers line from said trunk line, substantially as described.

58. In an automatic telephone system, a metallic circuit line, a substation in said line, a selecting switch for said line, controlling magnets for said switch, a disconnect magnet for said switch, a metallic circuit trunk line, means at said substation for causing the selecting switch of said line to select and connect with said trunk line. means for automatically disconnecting said controlling magnets from said line after such selection and connection. and means op erated over the limbs of said trunk line for closing the circuit of said disconnect magnet to cause said selecting switch to release said trunk, substantially as described.

59, In an automatic telephone system. a metallic circuit line, a substation and a selecting switch for said line, controlling magnets for said switch normally in operative relation with said line. a metallic circuit trunk line, means at said substation for causing its selecting switch to select and connect with said trunk line, means for automatically placing said controlling magnets in inoperative relation with said line after such selection and connection. relays connected with the limbs of said trunk, andmeans controlled by said relays for causing said selecting switch to disconnect said line from said trunk line, substantially as described.

60. In an automatic telephone system, a subscribers line, a metallic circuit trunk line. a selector serving to connect said subscribers line with said trunk line. controlling magnets for said selector, switches operated bv said controlling magnets to open the circuit of said magnets upon the completion of a selection, and electromagnet mechanism ineluding a third conductor trunk-release circuit controlled over the hne circuit to actuate SZLlClSQlQCtOl to disconnect said subscribers line "from said trunk line.

61. In an automatic, telephone system, a subscribers line, a selecting switch therefor, a trunk line, controlling magnets normally bridged across the subscribers line for causing said switch to select and connect with said trunk line, means for automatically disconnecting said controlling magnets from said line after their operation, a source cit current adapted to supply current over said trunk line to said subscribers line, and means including a third conductor trunk-release circuit operated by current from said source over said trunk line to cause said switch to disconnect said subscribers line from said trunk line, substantially as described.

62. In an automatic telephone system, a metallic circuit line, a substation in said line, a selecting switch for said line, controlling magnets for said switch, a disconnect magnet for said switch, a metallic circuit trunk line, means at said substation for causing the selecting switch of said line to select and connect with said trunk line, means for antomatically disconnecting said controlling magnets from said line after such selection and connection, and means including a third conductor trunk-release circuit operated over the limbs of said trunk line for closing the circuit of said disconnect magnet to cause said selecting switch to release said trunk, substantially as described.

63. In an automatic telephone system, a metallic circuit line, a substation and a selecting switch for said line, controlling magnets for said switch normally in operative relation with said line, a metallic circuit trunk line, means at said substation for causing its selecting switch to select and con nect with said trunk line, means for automatically placing said controlling magnets in inoperative relation with said line after suclr selection and connection, relays connected with the limbs of said trunk, and means including a third conductor trunkrelease circuit controlledby said relays for causing said selecting switch todisconnect said line from said trunk line, substantially as described. 7 Y

64. In a telephone system, a pair of subscribers lines including a metallic circuit connected by trunk lines at a central otlice, automatic selecting devices for said subscribers lines, and for each of said trunk lines, a pair of controlling magnets bridged across said metallic circuit line at one 0t said selecting devices, and means under control of said magnets for causing all off said selecting devices to return to their normal position and break the connection between said subscribers lines and said trunk lines,

one of said selecting devices having a wiper shaft with a third wiper thereon, said means including a release circuit through the said third wiper, and a busy test circuit including the same wiper, substantially as described.

65. In an automatic telephone system, a subscribers line, a selecting switch for said line at a central oflice, said switch having a wiper shaft with a third wiper thereon, a trunk line to which said subscribers line is extended by the movement of the selecting switch of said subscribers line, a selecting switch for said trunk line, a pair of controlling magnets for each of said selecting switches adapted to control the selecting movements of said switches, the magnets at the selecting switch of said subscribers line being in an open bridge across said subscrib ers line during a connection between said line and said trunk, said magnets in the selecting switch of said trunk being con nected in a closed bridge across said trunk during a connection with said line, and means associated with the selecting switch of said line, including a release circuit through the said third wiper, and controlled by the bridged magnets of the selecting switch of said trunk to cause the selecting switch of said line to assume its normal position, disconnecting said line iirom said trunk, and a busy test circuit including the same wiper, substantially as described.

66. In an automatic telephone system, a built-up circuit between two subscribers lines, selecting switches and'trunk lines in-- volved in building up said circuit, controlling magnets connected with said circuit at one of said selecting switches, other controlling magnets disconnected from said circuit at other of said selecting switches, said other switches each having a wiper shaft with a third wiper thereon, means including release circuits through the said third wipers, which circuits are at the switch having connected magnets for causing those switches having disconnected magnets to disconnect said built-up circuit, and busy test circuits in cluding the third wipers, substantially as described. 1 Y

67. In an automatic telephone system, a subscribers line, a first selector therefor, selecting contacts for said first selector, a trunk line adapted to be connected to said subscribers line by said first selector, a second selector for said trunk line, controlling magnets at said first and second selectors, means for energizing the magnets of said first selector to move said selecting contacts into engagement with said trunk line, a switch actuated by said magnets during their selecting operation to disconnect said magnets from said line, a release magnet for said first selector, a separate conductor individual to said trunk line, said first selector having a wiper shaft with a third wiper thereomineans including a release circuit through said third wiper, said circuit controlled by the magnets of said second selector, for causing the operation of the release magnet of said first selector over said separate conductor, and a busy test circuit including the third wiper, substantially as described.

68. An automatic telephone system comprising a temporarily established talking circuit, a selector relay bridge temporarily disconnected or cut ofl from the said circuit, a selector wi )er controlled by said bridge, a connector relay bridge retained across the said circuit for releasingpurposes, together with selector and connector releasing means, including a release circuit through said wiper, controlled by the said connector relay bridge, and a busy test circuit including Said wiper.

69. In a telephone exchange system, the combination of a talking circuit, a plurality of bridges on the conductors of said circuit, automatic means for reducing the number of bridges during talking, a shaft having a wiper associated with and allotted to one of said bridges, releasing means for disconnecting between subscribers, means for retaining one of said bridges to control the said releasing means, and a busy test circuit including said wiper.

70. In a telephone system, a pair of subscribers lines including a metallic circuit connected by trunk lines at a central office, automatic selecting devices for said subscribers lines, and for each of said trunk lines, a pair of controlling magnets bridged across said metallic circuit line at one of said selecting devices, and means under control of said magnets for causing all of said selecting devices to return to their normal positions and break the connect-ion between said subscribers lines and said trunk lines, one oi said selecting devices having a shaft with a plurality of wipers thereon, and said means including a release circuit through one of said wipers, substantially as deseribed.

71. In an automatic telephone system, a subscribers line, a selecting switch for said line at a central oflice, said switch having a shaft with a 1t lurality of wipers, a trunk line to which said subscribers line is extended by the movement of the selecting switch of said suhscripefis line, a selecting switch :t'onsaid trunk line, a, pair of controlling magnets for each of said selecting switches adapted to control the selecting movements of said switches, the magnets at the selecting switch of said subscribers line being in an open bridge across said subscribers line during a connection between said line and said trunk, said magnets in the selecting switch of said trunk being connected in a closed bridge across said trunk during a connection with said line, and means associated with the selecting switch of said line, including a release circuit through one of said wipers, and controlled by the bridged magnets of the selecting switch of said trunk to cause the selecting switch of said line to assume its normal position, disconnecting said line from said trunk, substantially as described.

72. In an automatic telephone system. a

built-up circuit between two subsc ibers lines, SlQCiZlIlQ' switches and trunk lines involved in building up said circuit, controh ling magnets connected with said circuit at one (it said selecting switches, other controlling magnets disconnected from said circuit at other of said selecting switches, Said other switches each having a shaft with a plurality of wipers, and means including release circuits through some of said wipers, which circuits are controlled at the switch having connected magnets, for causing these switches having disconnected magnets to disconnect said built-up circuit, substantially as described.

T3. In an automatic telephone systemfa subscribers l' a lirst selector theretor, sefor said first selector, a trunk line adapted t be connected to said subribel s line by said first selector, a second selector 'd trunk line, controlling magnets at said lust and second selectors, means for energizing the magnets of said first selector to move said selecting contacts into engagement with said trunk line, a switch actuated by said magnets during their selecting op -ration to disconnect said n'iagi'iets from aid line, a release magnet for said first selector. a separate conductor individual to said trunk line, said first selector hav-, ing a shaft with a plurality of wipers, and means including a release circuit through oneo't said wipers, said circuit controlled by the magnets of said second selector, tor causi' the operation of the release magnet oi said first selector over said separate com ductor, substantially as described.

telephone system com,-

T l. An. automatic prising a temporarily established talking circuit, a selector relay bridge te npn'arily disconnected or cut oil from the said circuit, a selector wiper controlled by said bridge, and a connector relay bridge retained across the said circuit for releasing purposes, together with selector and connector releasing means. including a release circuit through said. wiper, controlled by the said connector relay bridge.

T5. In a telephone exchange system, the combination of a talking circuit, a plurality of bridges on the conductors of said circuit, automatic means for reducing the number of bridges during talking, a. shaft having a wiper associated with and'allotted to one of said bridges, releasing means for disconne'cting between subscribers, said releasing means including acircuit through said wiper, which wiper is excluded from the tallc ing circuit, and means for retaining. one

' of said bridges to control 'flV} said releasing siredconnections,.tlie combination with a subscribers line, of a fil'SL selector switch adapted to be operated under substation con trol, second selector switches, multiple terminals'ot-said' second selector switches, and wipers included in. said. first selector switch adapted to engage said terminals, a part of said wipers be iiigt'or conversational use, a.

test wiper enabling said" first' selector to sehot. and isolate an idle second selector, means for causingja' flow of: current over said wiper when disconnection is desired, and release mechanism at the exchange operated responsive to" said flow.

78; It telephone system including a pair ot" connected subscribe-rs lines, a. plurality of selective switches at the exchange connecting said. lines, talking contacts included in said switches through which the conversational circuit extends, contacts included in some of.

said switches not foiming. part oft the conversational circuit with means controlled by saidcontacts: for preventing intrusion upon the connectioma relay atthe exchange controlla-b'le responsive to circuit. changes produced at the-calling substation, and means cont-rolledbys'aid relay for altering the connections of said last-mentioned contacts to release the switches.

79. A telephone system including a tele phone line, a selective switch at the exchange COHD'GCCEd with said 11116,.51 second selective switch connected with said first switch, contacts of said switchesforming' part or" a talking circuit, an additional contact piece for said first. switch in connection with a contact of said second switch serving to protect the talkingcircuit. froniintrusiom. means for altering the electrical COHClltlOIlof said". contact piece when disconnection is desired, and release mechanism for restoring a selective. switch responsive to said altered electrical condition;

8O. A telephone system including a telephone line, a-selectiveswitch.at the exchange tect the talking circuit froniintrusion, a re-.

leasei'elay, means responsive tov a. switch at. the substation of said. line for altering the operative condition. of said relay when disconnection is desired, switching mechanism.

coutrolled, by said relay. for. affecting, the:

electricalconditioii of said contact piece on alteration of SL1Cl operative condition. as descr bed, and. release apparatus responsive to the electrical.condition. of said contact piecev for restoring a selective switch.

81. A telephone, system including tele phone lines, interconnecting link-circuits and a selector switch for. extending the. talking circuit of a calling line to an idle link-circuit, said selector switch including a test contact for use in selecting the idle link-circuit, and means for restoring said switch to normal including a circuit. extendingthrough said testing contact.

82. A telephone. system including telephone lines, interconnectingv linlccircuits, a plurality of interconnecting automatic switch mechanisms for uniting calling and called lines by linkecircuits. into a talking circuit, testing contacts associated with certain of said. switch mechanisms for use in determining the link-circuits to be included in said talking circuit, means for releasing one of said. switch mechanisms, a circuit in cluding. a testing contact, and means operated by said releasing means over said cir cult to release another of said switchmechanisins.

83. A telephone system including telephone lines, interconnecting link-circuits, a plurality of. selective switch mechanisms for uniting. a calling and a called line by link-circuits into a talking circuit, a private. contact associatedv withone of said switch mechanisms, a connection device for contact therewith to place a busy potential upon said contact to protect the talking circuit from intrusion, a release circuit for one or said switching mechanisms including'said private contact, and apparatus for altering the potential of said private contact when discon nection is desired to render said release circuit ettective.

84. A telephone system including tele phone lines, interconnecting link-circuits, selector"and connector switches for uniting. calling and called lines by certain of said link-circuits into a talking circuit, said selector and connector switches being providedwithtesting contacts for use in determining the talking circuit, and means for releasing said selector switch including a circuit through its testing contact in response to the release 01": said connector switch, and means for releasing the latter,

85. A telephone system including a telephone line, a selective switch at the exchange connected with said line, a second selective switch connected with said first switch, contacts of said switches forming part of a talking circuit, an additional contact piece for said first switch in connection with a contact of said second switch serving to protect the talking circuit from intrusion, a release relay, means for altering the operative condition of said relay when disconnection is desired, and release mechanism responsive to an altered electrical condition of said contact piece produced responsive to said relay for restoring a selective switch.

86. An automatic telephone system comprising a first selector, a second selector and a connector, a release-circuit for the first selector, together with means for supplying all necessary current, said second selector being provided with a release-magnet di rectly controlling the release and also controlling a normally-open switch point in said release-circuit.

87. In a telephone system, an automatic switch, a pair of line wipers, a third wiper therefor, a side switch having a plurality of positions, a relay, means for connecting said wiper to ground through said relay when the said side switchpasses to third position, and a release magnet for controlling the release of said switch, the circuit of said release magnet being controlled by the first mentioned relay.

88. In a telephone system, subscribers lines divided into groups, an automatic switch having motion in one plane to select groups, and motion in a plane at right angles thereto to find a line in the selected group, a pair of line wipers, a third wiper therefor, a side switch having a plurality of positions, a relay, means for connecting said third wiper to ground through said relay when said side switch passes to third position, and a release magnet for controlling the release of said switch, the circuit of said release magnet being controlled by said first mentioned relay.

89. A telephone system comprising a selector provided with a side switch, a release relay for releasing said selector while .the said switch is in first or second position,

and a release relay for releasing the said selector when the said switch is in third position.

90. A telephone system comprising automatic trunk selectors, automatic connectors provided with means having vertical motion from one operative level to another to select groups or divisions of the exchange, and rotary motion in any selected level to connect with a line therein, trunk release circuits :t'or the selectors controlled by the connectors, a calling device at each substaducing the number oi bridges across the talking circuit during the establishment thereof, automatic connectors, trunk release circuits for the selectors controlled by the connectors, and a source of operating current, said connectors each provided with one or more permanently bridged line relays each permanently connected with said source of current.

92. In a telephone exchange system substantially as disclosed, the combination of a selector having release mechanism, the conneetor provided with a pair of line relays controllable over any calling subscribers line to extend a connection to a called telephone line, said connector having release mechanism, there being a trunk release circuit extending between the selector and the connector for controlling the release of the connection, said release circua't having a plurality of normally open switch points, said relays being retained under the control of the calling subscriber for changing the condition of one of said switch points while. the called telephone is closed across the connection for talking, a subscribers impulse transmitter or calling device for transmitting to the exchange or central station the electrical impulses representing the number of any called subscriber.

93. In a telephone exchange system substantially as disclosed, the combination of a selector having release mechanism, a connector provided with a pair of line relays controllable over any calling subscribers line to extend a connection to a calledtelephone line, said connector having release mechanism, and there being a trunk release circuit extending between the selector and the con neetor for controlling the release of the connection, said release circuit having a plurality of normally open switch points, the condition of one of the switch points subject to be changed by the calling subscriber while the called telephone is closed across the connection for talking, and subscribers impulse transmitters or calling devices for transmitting to the exchange or central station the electrical impulses representing the number of any called subscriber.

94. An automatic telephone system comprising a battery, a trunk-line terminating in contacts, said contacts having a suitable number of multiples, an additional contact and a suitable number of multiples thereof, an automatic switch provided with means for engaging said trunk-line contacts, and provided also with means for connecting one pole of said battery with said additional contacts for the purpose of preventing seizure by other parties ot'the said trunk-line when in use, and a release circuit for said switch including said additional contacts.

95. An automatic telephone system comprising an automatic switch provided with a guarding potential circuit and also with a releasing circuit, and having a switch-contact included in both of said circuits, and means for closing said releasing circuit to disconnect two connected subscribers.

96. An automatic telephone system comprising a subscribers line, a selector-switch individual to said line, a trunk-line termi-, nating in the contacts of said switch, and a connector-switch permanently with the other end of said trunk-line, together with means includingan additional trunk-line conductor for releasing the said selector switch, the releasing circuit being provided with a normally open switch-point controlled by an element of the said connector-switch.

97. An automatic telephone system comprising switching apparatus including aprivate bank-contact, a normally open switch connected with said private bank-contact, a battery having one pole connected with said normally open switch, means for operating said switch, said normally. open connection between the battery and said private bankcontact including a suitable resistance, the other pole of said battery being grounded, a private wiper adapted to engage said contact, and means for grounding said wlper when the switching apparatus is in use, the normally open connection between said wiper and ground including a relay-coil of less resistance than the said resistance in the normally open connection between the battery and the said contact, togetherwith one or more multiples of said contact.

98. An automatic telephone system comprising a trunk-line, a selector-switch adapted to make connection with one end of said trunk-line, said selector-switch having a release magnet and a release relay, another switch connected with the other end of said trunk-line, said other switch having a release magnet and a private magnet, means for furnishing all necessary current, and a release circuit for effecting the release of said selector-switch, said release circuit having a normally open switch-point controlled by the release magnet of said other switch, and having two other normally open switchpoints controlled by said selector switch, the said release relay controlling the operation of the release magnet of the selector switch, and the private magnet of the said other switch controlling the said release magnet thereof.

connected 99. An automatic telephone system comprising a normally open talking circuit, a bridge normally connected across said circuit, means for cutting off or opening said bridge, said circuit being at all times free from inductive resistance in the path of the voice currents, and a'trunk-release circuit extending parallel with an intermediate portion of said circuit and controlled at the end. thereof toward the calling subscriber.

100. An automatic telephone system comprising an automatic trunk-selecting switch mechanism provided with releasing means, a connector-switch provided with releasing means including a release-magnet, and a release circuit for operating the releasing means of the trunk-selecting switch mechanism, said circuit being controlled by the said release-magnet of the connector.

101. In a telephone system, a switching machine, another switching machine, a release circuit connecting said switches, a source of switching current, other switches, and means for supplying a guarding potential from one pole of said battery to said other switches over a portion of said release circuit.

102. In a telephone system, a movable switch-contact, a normally open release circuit including said contact, means for closing said release circuit to disconnect two connected subscribers, and a normally-open busy-circuit which also includes said contact.

103. An automatic telephone system comprising switch-release mechanism, a releasemagnet for operating said mechanism, a swinging switch wiper, normally open switch-contacts operated by the energizing and deenergizing of said release-magnet, a trunk-lineconductor, and a normally-open circuit including said swinging switchwiper and normally-open contacts.

104. An automatic telephone system comprisinga switching machine having electrically-propelled and step-by-step switching mechanism, and having a pair of line-relays for. controlling said mechanism, and another switching machine having release mechanism controlled by a release-relay, together with a releasecircuit between switches including said relay, and means whereby the closing of said circuit toenergize the said relay and thereby operate its release mechanism is ac-., complished by the simultaneous energizing of said line-relays.

105. An automatic telephone system comprising a first-selector provided with a release-relay, a second-selector provided with a pair of line-relays, a battery for furnishing the current necessary for operating said selectors, and an energizing circuit for said release-relay controlled conjointly by said line-relays.

106. An automatic telephone system comprising a seiextor provided with a releaserelay, a. connector provided with a pair of llIlG-I'Qlt1' S, means for supplying the necessary current, and an ener 'izing circuit for said release-relay, controlred conjointly by said line-relays.

107. In an automatic telephone system, a metallic circuit subscribers line, a metallic circuit trunk line to which said subscribers line is adapted to be extended, selecting switches for said subscribers line and said trunk line, controlling-magnets for each of said selecting switches connected respectively with said subscribers and trunk lines, and means 1'01 causing the selecting switch of said line to connect said line with said trunk, and to simultaneously disconnect said controlling magnet from said line, substantially as described.

108. The combination with a telephone station, a pair of wires leading from the station to a central ofiice, and a pair of wipers located at the central office and normally dis connected from said wires, of a series of trunk connections, magnets operable by im pulses sent over said wires to bring about a movement of said wipers to select a non-busy trunk connection, and means by which upon said wipers finding a non-busy trunk connection non-inductive connections will be autoi'i'iatically completed from said station to said wipers.

109. The combination with a telephone station, a pair of wires leading from the station to a central oflice, and a pair of wipers at the central office and normally disconnected from said wires, of a series of trunk liner, means for moving said wipers so as to select a non-busy trunk line, and means by which upon said wipers finding a non-busy trunk line non-inductive connections will be automatically completed between said stations and said wipers Signed by me at Chicago, Cook County, Illinois, this 9th day of January, 1905.

ALEXANDER E. KEITH. 

